Mechanical rectifier



L. BRADLEY.

MECHANICAL RECTIFIER.

APPLICATION man FEB. 14. 1919.

430 1 9 Patented Oct. 3, 1922.

Patented Oct. 3, 1922.

UNITED STATES PATENT OFFICE.

LINN BRADLEY, 01 EAST ORANGE, NEW JERSEY, ASSIGNOR TO RESEARCH CORPO-RATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MECHANICAL RECTIFIER.

Application filed February 14, 1919. Serial No. 277,019.

To all whom it may concern:

Be it known that I, LINN BRADLEY, a citizen of the United States,residing at East Orange, in the county of Essex and State of New Jersey,have invented certam new and useful Improvements in MechanicalRectifiers, of which the following is a spec fication.

The present invention relates to mechamcal rectifiers.

Mechanical rectifiers, especially those of the contact type, have theserious drawback that destructive arcin takes place because of theimpossibility 0 always commutating the current at the precise instantwhen the electromotive force is zero. This is especially the case inconnection with load de vices having a variable inductance or capacity.

Bectifiers'are extensively used to convert high tension alternatingcurrent into unidirectional current to charge electric precipitators. Anelectric precipitator is, as is well known a leaky condenser ofconsiderable capacity. Relatively slight disturbances in theprecipitator chamber cause a disturbance of the phase relations betweencurrent and voltage, and a disturbance of the phase relations manifestsitself by sparking at the commutator or rectifier brushes. Sparking inturn adds to the disturbance in the treater chamber and so on, so thatsmall disturbing causes ma result in surges and oscillations which worhavoc in the treater chamber and at the rectifier apparatus.

In the past much trouble has resulted from charring of insulation due tothe destructive sparkingbetween adjoining seg-- ments or contacts on therectifier disk, which segments have been made of rectangular sha c.

It is the object of this invention to reduce destructive arcing as muchas possible and at. the same time to cause the arcing to take place at apoint on the rectifier where it cannot do any harm to the insulation orto the contacting surface.

The object, operation and result of the invention will appear moreclearly from detailed description in connection with the accompanyingdrawings, in which Fig. 1 is a side view of what I consider at presentas the preferred embodiment of the invention;

. rate assembly.- To this modified or changed generally of the diskpassing Fig. 2 is an end view thereof;

ig. 3 is a view. similar to Fig. 1 showing a (silightly modified use ofthe invention; an

Figs. 4-9 show modifications of a detail. In the drawing 1 represents arectifier disk made in the usual manner of insulating material, such asmicarta, glass or other well known substances. The disk is preferablymade in two parts so as to permit sepaend the two halves of the disk areprovided with flanges 2 by means of which the may be clamped togetherupon the sha t- 3. Spacers 4 may be used to aflordarigid connectionwithout straining the material. These details are not material to'theinvention and may be as desired. Along the periphery of the disk aredisposed contact segments 5 and 6 which are similar to the segmentsusually employed to establish by contact with stationary contact shoes7, 8, 9 and 10 electrical connection between the source of current andthe load device in the well known manner. Adjacent the trailing end ofthe segments 5 and '6 and spaced therefrom are auxiliary contact members11 and 12 respectively. The segments and the auxiliary contact membershave overhanging portions 5, 6, 11' and 12' respectively to define freespaces therebetween and the edge of the disk. In these spaces aredisposed horn-gap devices 13 and 14.- respectively. One horn of eachdevice is connected to one of the segments and the other to the adjacentauxiliary contact member. The horn-gap devices are so positioned thatthe axis of each lies substantially at ri ht angle to a radius t roughit. In other words, the horn-gaps have their axes in the direction ofmotion of the disk with the result that the relative velocity of the airpassing through the gaps is substantially equal to the peripheralvelocity of the disk.

The operation of the device so far described is obvious. The disk isrotated in the direction of the arrow. As the trailing end of thesegments leaves the stationary shoe, the electromotive force, if itshould have at that time a value considerably above zero, tends tomaintain the current flow in the form of an arc. The are is sustained inproportion to the value of the electromotive force. .Since the horns ofthe horngap mechanism are relatively close together, an

.. latter and the position thereof may to judgment or particular re-'are is established therebetween when the distance between the trailingend of the segment and the stationary shoe becomes greater than thehorn-gap. As the distance between the segment and the stationary shoeincreases, the arc is entirely shifted to the horn-gap where it is thenguished by the well-known orn-gap action hastened by the action of theair current rushing through the gap.

A second set of auxiliary contact mem;

bers and 16 together with a second set of hornap mechanisms 17 and 18may be employe in addition to the previously described devices.

put closer together and the horns ofthe hornap mechanisms 17 and 18 arebrough still closer together.

By the arrangement described not only the arcing between the stationarycontact shoe and the contact elements on the dlsk,

but also between the adjacent contact ele-' ments on the disk is reducedand such arcing as cannot be avoided is shifted to a point away from theinsulation and from the contacting surface.

In Fig. 4 is shown an S-shaped element connected to one side of acontact-element 31 on the disk and extending. close to the precedincontact element 31 in such a way as to orm a horn 32 defining. a sparkap. 4 f In. ig. 5 is shown a spark gap formed between two spheres 33 inthe space between adjacent contact elements 34 and 34' away from theinsulation.

' Figs. 6 and 7 show spheres supported on arms 36 extending away fromthe contact elements in lateral direction.

In Figs. 8 and 9 a horn-ga is formed by elements 37 attached to the sies of the overhanging shoulders 38.

It is understood that the number of auxiliary contact members neednot berestricted to two. The number of such auxiliary elements and horn-gaps,the spacing of the e varied according quirements.

It is also understood-that the length of the segments may be varied inaccordance with the portion of the alternating current wave to berectified.

In Fig. 1, I have shown the segments long enough to span the stationarycontact shoes. However, I contemplate also the shortening of thesegments to such an extent that commutation takes place with one or moreof the horn-gaps in circuit as shownin Fig. 3. The segment 20 subtendsan angle of less than 90 and' therefore does not s an the stationarycontacts 21 and 22. In t e position shown the current passes say fromthe uickly extin- In this case the horns of the horn gap mechanisms 13and 14 may be i stationary contact shoe 21 through the segment 20, thenthrough the horn-gap mechae nism 23 to the auxiliary contact member, to

contact shoe 22 and to the load devlce' (not shown) while the returncurrent coming from the load device passes through the stationarycontact shoe 24 to the auxiliary contact member 25, then through thehorn-gap mechanism 26 to the segment 27 and then to the source ofcurrent. Thus an air ga is initially introduced into the circuit an assoon as the stationary contact shoes leave the trailing end of theauxiliary contact members the second set of horn gap mechanisms 28 and29 is introduced into the circuit.

I have further shown the air ga between two opposed segments to, be 0less resistance than the leakage path over the insulation; therefore abreak-down will take place from conductor to conductor throu h the airin preference to leakin over t e surface of the insulating materia ofwhich the. disc is made.

a rotary disk of insulating material and a metallic'segment thereonadapted to contact with the stationary shoe an auxiliary metalliccontact member on the disk spaced from the segment, and means fordefining between the segment and theauxilia contact member at a pointaway from tlie contact surfaces thereof an air gap which is smaller Thlseliminates possi-- bllltiy of leakage, sparking or arcin near gaps andnumthan the distance between the segment and I the auxiliary tactsurfaces.

2. In a mechanical-contact rectifier the combination of a stationarycontact shoe, a rotary disk of insulating material and a metallicsegment thereon adapted to contact with the stationary shoe, anauxiliary metallic contact member on the disk spaced from contact memberat their conthe segment, and means for defining between the segment andthe auxiliary contact member at a point away from the edge of the diskan air gap which is smaller than the space between the segment and theauxiliary contact member near the periphery of the disk.

3. In a mechanical-contact rectifier the combination of a stationarycontact shoe, a rotary disk of insulating material and a of the disk anair gap which is smaller than the space between the segment and theauxiliary contact member near the periphery of the disk and extendssubstantially in a radial direction.

4. In a mechanical-contact rectifier the combination of a stationarycontact shoe, a rotary disk of insulating material and a metallicsegment thereon adapted to contact with the stationary shoe, anauxiliary metallic contact member on the disk spaced from the segment,and means for defining between the segment and the auxiliary con- 20tact member at a point away from the con-.

tact surfaces thereof an air gap which is smaller than the distancebetween the segment and the auxiliary contact member at their contactsurfaces and extends substantially in a radial direction.

5. In a mechanical-contact rectifier, the combination of a stationary.contact shoe, a rotary disk of insulating material and a metallicsegment thereon adaptedto contact with the stationary shoe, an auxiliarymetallic contact member on the disk spaced from the se ent and ahorn-gap mechanism interme iate the segment and the auxiliary contact,member.

6. In a mechanical-contact rectifier, the combination of a stationarycontact shoe, 8. rotar disk of insulating material and .a meta licsegment thereon adapted to contact with the stationary shoe, anauxiliary metallic contact member on the disk spaced from the se ent,and a horn-gap mechanism interme iate the segment and the auxiliarymember having one horn connected to the former and the other horn to thelatter.

7. In a mechanical-contact rectifier, the combination of a stationarycontact shoe, a rotar disk of insulating material and a meta lic segmentthereon adapted to contact with the stationary shoe, an'auxiliarymetallic contact member on the disk spaced from the se ent, and ahorn-gap mechanism interme iate the segmentand the auxiliary memberhaving one horn connected to the former and the other horn to thelatter, the axis of the horn gap mechanism lying substantially at rightangles to a radius of the disk assing through it. v

8. n a mechanical-contact rectifier, the combination of a stationarycontact shoe, a rotary disk of insulating material and a metallicsegment thereon adapted to contact with the stationary shoe,- anauxiliary metallic contact member on the disk spaced from the segment,the said segment and auxiliary contact member havin adjacent to eachother overhanging portions defining a free space therebetween and theedge of the disk.

9. In a mechanical-contact rectifier, the

combination of a stationary contact shoe, a

rotary disk of insulating material and' a metallic segment thereonadapted to contact with the stationary shoe, an auxiliary metalliccontact member on the disk spaced from the segment, the said segment andauxiliary contact member having adjacent each other overhanging portionsdefining a free space therebetween and the edge of the disk, and meansfor defining between the segment and auxiliary contact member at a pointaway from the edge of the disk an air gap which is smaller than thedistance between the overhanging shoulders.-

10. In a mechanical rectifier, the combination of stationary contactshoes, a rotary disk of insulating material, metallic segments thereonadapted to contact with the stationary shoes and auxiliary metallic contact members disposed in spaced relation along the periphery of the diskintermediate the said se ents and air gap mechanism between an formingpart of adjacent contact members.

11. In a mechanical rectifier, the combination of stationary contactshoes, a rotary disk of insulating material, metallic segments thereonadapted to contact with the stationary shoes, auxiliary metallic contactmembers disposed in spaced relation alon the periphery of the diskintermediate t c said segments and means for varying the electricresistance between the segments and the separate auxiliary contactmembers.

12. In a mechanical rectifier, the combination of. stationary contactshoes, a rotary disk of insulating material, a plurality of 'metalliccontact elements disposed in spaced ture.

' LINN BRADLEY.

